Scientific Method —

Composite material brings metal-air batteries a step closer

New catalyst allows metal-air batteries to breathe easier.

As a society, we are now heavily dependent on good battery technology. Indeed, as climate change starts to bite and hydrocarbon fuels become more expensive, the demand for better batteries is just going to increase. But the current best technology is simply not going to keep pace. Commercial Lithium ion batteries are approaching their theoretical maximum energy storage density, which is lower than that of gasoline by a factor of about 60-70. In the meantime, we want electric cars like the Tesla—but lighter, with longer range and faster recharging times.

One solution to some of these problems may be metal-air batteries. These batteries have maximum energy densities approaching that of gasoline. Better than that, they should be simpler to construct and could even be made from cheaper materials. In other words, when viewed through rose-tinted glasses, metal-air batteries are better in every way.

The problem is that no one knows how to make one that meets all of these criteria. A group of chemists from University of Waterloo in Canada may be heading in the right direction, though.

One of the big obstacles is getting the oxygen in the right form before it meets the metal. We want that metal to oxidize, but without a spectacular display of pyrotechnics. The way to control the reaction and use some of its energy is to find the right catalyst. A catalyst is a material that, simply put, gives reactions a helping hand.

A reaction is, at heart, just the transfer of electrons—in a battery we just make the electrons do some work along the way. At one electrode, electrons are given up when a metal is oxidized. These electrons travels out of the battery, get put up at a local capacitor, do some work, and return to a different electrode in the battery. Back in the battery, the electrons are used in a reaction that frees up oxygen to react with the metal at the other electrode.

In other words, we have two circuits. In one circuit, electrons flow and do work, while in the other, oxygen flows to generate and receive electrons. The big problem in this scheme is to get something like atomic (rather than molecular) oxygen around to react, and later on, convincing the oxygen to let go of the metal so you can recharge the battery.

We need a catalyst that will convince an oxygen molecule to split up to form some sort of radical (either a lone oxygen atom, or, more commonly, a reactive OH). Then, to allow recharging, we want a second catalyst that recombines oxygen atoms to make molecular oxygen. Traditionally, these catalysts are mixtures of things like palladium and platinum, along with other expensive metals. What is more, they tend to degrade with time, producing a battery that isn't cheap, and doesn't last for very long.

So, one of the big efforts in the field at the moment is the development of a catalyst that is stable and cheap. Various lines of earlier research have shown that metals like nickel and cobalt could make good catalysts for producing molecular oxygen, while carbon-based materials seem to make pretty good oxygen reducing catalysts. The trick, then, is to turn these into stable and efficient catalysts. This is where this latest bit of research comes in.

The researchers noted that a particular crystalline form of oxides, called perovskites, make a good support structure for the growth of carbon nanotubes—that is, if you grow nanotubes in their presence, the nanotubes grow all over the oxide material. They also noted that nitrogen doped nanotubes are, chemically, quite stable, making them a good candidate for the oxygen reducing catalyst. By using a dollop of nickel in the perovskite structure, instead of lanthanum oxide, they could create a lanthanum-nickel-oxide catalyst, one that would also support the growth of a carbon-based catalyst.

The key, however, is to make sure that you have lots of surface area available for both catalysts. To achieve this, the researchers created nano particles of the lanthanum nickel oxide, then used these to host nitrogen-doped nanotubes, creating the worlds smallest, hairiest balls.

The catalyst was then coated on one electrode of a zinc battery for testing. First the bad news: the stored energy drops by about 22 percent compared to a zinc battery that uses precious metal catalysts. From there on, though, the news seems to be good. The catalyst seemed to be pretty efficient—that is, it didn't require huge voltages to get it to recharge and provided a reasonable current-voltage curve when discharging. But more importantly, it appeared to be much more stable than previous options.

In a test of 75 cycles, one could see that the comparison batteries were already beginning to fail, while the battery with the new catalyst was still functioning OK. Of course, 75 cycles is not a lot, and there was still a minor change in charge-discharge characteristics over even that short a time. That could simply be the battery settling to some steady-state, but more likely it is the beginning of a death spiral from which it never recovers.

The cynical amongst us will say, "Bah, 75 cycles? Call me when they reach 1,000." I, on the other hand, see this as great progress. I wouldn't bet on metal-air batteries going into new devices within three years, but you certainly won't have to wait ten for them to turn up.

Chris Lee
Chris writes for Ars Technica's science section. A physicist by day and science writer by night, he specializes in quantum physics and optics. He lives and works in Eindhoven, the Netherlands. Emailchris.lee@arstechnica.com//Twitter@exMamaku

If electric-anything is going to replace burning fossil fuels in our cars or other things then it's going to require dramatically better battery technology then we have now. If people think that locating refining fossil fuels is a insurmountable problem long-term then they haven't seen what it takes to produce lithium batteries...

But this may not be an issue. The recharge time is largely a function of the mechanical arrangement of the batteries, and we already have a couple of hot leads on ways to address this. The same mechanical issue also limits the discharge rate, which limits power.

Personally, I would be perfectly happy with a car that gets a range of about 65 miles, which covers about 95% of all my round-trips - and everyone else's.

For the other 5%, the car company could sign a deal with a rental company to arrange a keys-in-keys-out rental process. That is, I have already provided all the information the rental company needs when I bought the car. I simple drive up, plug in my car, pick the otherwise identical gas-powered version, use my key and off I go. More business for the rental company, less paperwork, no range anxiety. Everyone wins.

Hell yeah battery technology. I swear that between awesome batteries, advanced thin-film solar power and the smart-grid upgrades, in 20 years everyone is going to be slapping their foreheads at how stupid everything (is now) used to be.

If electric-anything is going to replace burning fossil fuels in our cars or other things then it's going to require dramatically better battery technology then we have now.

Balogna. How many miles did you put on your car last year? Divide that by 365. Is the result less than 100? Then we already have all the technology we need.

In fact, the thing that's actually made the electric car practical is not the batteries, but the inverters. IGCT's have *dramatically* changed the nature of the problem, and resonant conversion might do the same again.

drag wrote:

If people think that locating refining fossil fuels is a insurmountable problem long-term then they haven't seen what it takes to produce lithium batteries...

I just knew platinum would play a part the moment you said a catalyst was needed however the platinum price is usually more than the gold price at any given time except now. The idea you can substitue perovskites, carbon nanotubes and making things small for it is nice.

If electric-anything is going to replace burning fossil fuels in our cars or other things then it's going to require dramatically better battery technology then we have now.

Balogna. How many miles did you put on your car last year? Divide that by 365. Is the result less than 100? Then we already have all the technology we need.

Averages don't mean squat. Quick math tells me I drive about 77.62km per day. However, I can go a few days without driving, and often I need to make out of town trips where I'll put in 600-1000km in a day.

I may not be the norm, but averages are misleading when it comes to battery technology and driving. Finding yourself stranded somewhere without the ability to recharge because you were sold on your average daily use is little comfort.

But this may not be an issue. The recharge time is largely a function of the mechanical arrangement of the batteries, and we already have a couple of hot leads on ways to address this. The same mechanical issue also limits the discharge rate, which limits power.

Recharging batteries has more to do with what power you can get access to. I'm going to have a 220V/15A (3.3kW) charger installed for my new Chevy Volt soon in my garage, and that will bring down my full-charge time to 3-4 hours (from 8-9). For most people in their garage at home (where charging takes place), you wont be able to go much beyond 6.6kW (220V/30A) because electrical service to houses typically have 75 or 100A access (all this assumes you have a garage, which is another issue). Even if you plug-in at an EV charging station, you aren't going to be able to pull the almost 1MW of power you'd need to recharge a new Tesla Model S battery from 0 to 100% in 5 minutes.

One thing to keep in mind is that batteries are needed for a lot more than automobiles (though a good, cheap battery there would be a game-changer). Another huge area for use would be the electric grid. (Of course, I wouldn't complain about a 10x increase in storage density for electronics, either, let alone 60-70x.)

Having a good battery technology to plug into the grid would enable fundamental changes that would save a lot of energy, provided they have a reasonable ratio of (cost)/(storage density). Currently a lot of energy is wasted simply because all electricity must be used as soon as it is generated, so even a small amount of storage capacity to smooth-out variations in demand would be appreciated. The larger the amounts of storage, the better engineers could optimize the system.

But this may not be an issue. The recharge time is largely a function of the mechanical arrangement of the batteries, and we already have a couple of hot leads on ways to address this. The same mechanical issue also limits the discharge rate, which limits power.

Recharging batteries has more to do with what power you can get access to. I'm going to have a 220V/15A (3.3kW) charger installed for my new Chevy Volt soon in my garage, and that will bring down my full-charge time to 3-4 hours (from 8-9). For most people in their garage at home (where charging takes place), you wont be able to go much beyond 6.6kW (220V/30A) because electrical service to houses typically have 75 or 100A access (all this assumes you have a garage, which is another issue). Even if you plug-in at an EV charging station, you aren't going to be able to pull the almost 1MW of power you'd need to recharge a new Tesla Model S battery from 0 to 100% in 5 minutes.

You could certainly bypass electrical service power limitations by including batteries as part of the charging station. While the car is out expending its energy, the charging station can be replenishing its own.

But this may not be an issue. The recharge time is largely a function of the mechanical arrangement of the batteries, and we already have a couple of hot leads on ways to address this. The same mechanical issue also limits the discharge rate, which limits power.

Recharging batteries has more to do with what power you can get access to. I'm going to have a 220V/15A (3.3kW) charger installed for my new Chevy Volt soon in my garage, and that will bring down my full-charge time to 3-4 hours (from 8-9). For most people in their garage at home (where charging takes place), you wont be able to go much beyond 6.6kW (220V/30A) because electrical service to houses typically have 75 or 100A access (all this assumes you have a garage, which is another issue). Even if you plug-in at an EV charging station, you aren't going to be able to pull the almost 1MW of power you'd need to recharge a new Tesla Model S battery from 0 to 100% in 5 minutes.

You could certainly bypass electrical service power limitations by including batteries as part of the charging station. While the car is out expending its energy, the charging station can be replenishing its own.

That, sir, is a winning idea. You should really do something with that....

You could certainly bypass electrical service power limitations by including batteries as part of the charging station. While the car is out expending its energy, the charging station can be replenishing its own.

Correct me if I'm wrong, but last I checked the discharge rate on most batteries is quite limited, at least in part due to the chemical and consequently thermal interactions that take place in the process, so this wouldn't really help unless you want the charging station to explode when someone wants to recharge their car. A supercapacitor would be a different story, but that's not practical at this point either.

If electric-anything is going to replace burning fossil fuels in our cars or other things then it's going to require dramatically better battery technology then we have now.

Balogna. How many miles did you put on your car last year? Divide that by 365. Is the result less than 100? Then we already have all the technology we need.

Averages don't mean squat. Quick math tells me I drive about 77.62km per day. However, I can go a few days without driving, and often I need to make out of town trips where I'll put in 600-1000km in a day.

I may not be the norm, but averages are misleading when it comes to battery technology and driving. Finding yourself stranded somewhere without the ability to recharge because you were sold on your average daily use is little comfort.

For single people, this is often likely to be a dealbreaker. For two-car married couples, it may be practical to get one efficient short-range commutermobile and one long-range vehicle.

But I agree that Americans are used to being able to go on driving trips (Mount Rushmore! the Grand Canyon! Yellowstone!) enough that simply accepting a 100 mi range as a core limitation of cars is not going to happen as long as any possible alternative exists.

As an owner of a Nissan Leaf, I'm not as concerned about both increasing range and shortening charge time. One of them mitigates the problems of the other.

While having both would be fantastic, I could deal with the slow charge time of even our 220V charger if the car had a range of, say, 200 real-world miles. Our Leaf has a real-world range of about ~70 miles. While that's fine for my wife's daily commute downtown. But any time she has to visit a client we have to switch cars so she can use my huge gas-powered family vehicle. If it weren't for the short range it would be a nearly perfect commuter car.

I would happily get rid of my large gas-powered car for something like a Tesla Model X if the charge cycle were faster (and we had the money for it). I have no qualms about trading cheaper operating costs and a more efficient and pleasant ride 50 weeks of the year for the requirement of renting a minivan for the 2 possible weeks when we might need a car for a road trip.

Give me a similar range but a recharge time of less than an hour and I'm fine. Give me a range of 250 miles and I'm fine with the longer recharge cycle. Give me both and make it cheaper? Sign me up and take my trade-in.

You could certainly bypass electrical service power limitations by including batteries as part of the charging station. While the car is out expending its energy, the charging station can be replenishing its own.

Correct me if I'm wrong, but last I checked the discharge rate on most batteries is quite limited, at least in part due to the chemical and consequently thermal interactions that take place in the process, so this wouldn't really help unless you want the charging station to explode when someone wants to recharge their car. A supercapacitor would be a different story, but that's not practical at this point either.

I was addressing the specific problem of electric service limitations. There will always be charging limitations, and overcoming electric service limitations in a way that also smooths demand seems like a reasonable alternative to rebuilding the entire electric infrastructure.

BTW, it is also possible to physically swap out depleted batteries for charged ones.

But this may not be an issue. The recharge time is largely a function of the mechanical arrangement of the batteries, and we already have a couple of hot leads on ways to address this. The same mechanical issue also limits the discharge rate, which limits power.

What? No. Just.. No.... Recharge time is largely a function of safety, and preventing damage to the battery. We reduce the capacity of Lithium Ion batteries in cars for safety, using less energy dense cathodes such as lithium iron phosphate instead of lithium cobalt oxide. Even then, the electrolyte in lithium Ion batteries forms deposits that increase the internal resistance, this is going to happen with time no matter what, but extra heat helps this process along. Fast charging heats up the carbon anode, so you're going to be limited on charge time just to avoid heat... and the possibility of thermal runaway. This is a chemistry problem not mechanical arrangement....

Correct me if I'm wrong, but last I checked the discharge rate on most batteries is quite limited, at least in part due to the chemical and consequently thermal interactions that take place in the process, so this wouldn't really help unless you want the charging station to explode when someone wants to recharge their car. A supercapacitor would be a different story, but that's not practical at this point either.

I was addressing the specific problem of electric service limitations. There will always be charging limitations, and overcoming electric service limitations in a way that also smooths demand seems like a reasonable alternative to rebuilding the entire electric infrastructure.

BTW, it is also possible to physically swap out depleted batteries for charged ones.

Having a Battery/Super Capacitor bank at home to lower you're impact on the utilitie's infrastructure would not be a bad idea. If you had a battery bank of the same batteries in your car, you could keep them cool and provide them charge/discharge cycles for longer life, that way you always have good batteries to replace poor performing batteries in your car, to maintain the best car performance.

Do you think this is the most important thing for our children to be still alive after probably 20 years? Were all so stupid that "superior product to market for a cheaper price" was only the idea of their life?

Do you think this is the most important thing for our children to be still alive after probably 20 years? Were all so stupid that "superior product to market for a cheaper price" was only the idea of their life?

I'm their manufacturer, I decide their fate!MUAHAHAHAHAHAHAHA. No Refunds, No warranties implied.

Correct me if I'm wrong, but last I checked the discharge rate on most batteries is quite limited, at least in part due to the chemical and consequently thermal interactions that take place in the process, so this wouldn't really help unless you want the charging station to explode when someone wants to recharge their car. A supercapacitor would be a different story, but that's not practical at this point either.

This. Most batteries have specific rates they can be efficiently charged at, without damaging - and specific discharge rates.

I don't know the specs for Lithium Ion, but there is a reason laptop powerbricks aren't 200W - the batteries cannot handle that charge rate. I've read that they have similar charging curves to lead acid.

One tech that I've wondered if it could be adapted (probably not, because it hasn't already) is AGM (Absorbed Glass Matt), which I have in my RV. I don't recall the specifics, but normal lead acid car batteries (also often used in Deep Cycle marine or RV) can be charged at only 1/4 discharge capacity. So, with a "fast" charge, it takes 4x as long to charge as its max rated discharge.

AGM, on the other hand, theoretically has no limits. I can charge my RV battery at 4x discharge rate, so 16x as fast as a lead acid battery - and more, and I'd need a bigger power source (not that the battery is the limiting factor). Sure, it cost like 3x as much, but worth it.

I've got a bypass on my camper's converter, so I hook my generator up, fire it up, and pump 12V through the camper's "normal" power (to power lights, etc), and another 70 amps (at 12v) straight into the battery... which is a 100Ah @ 12V battery... so fully charged in 1.5 hours.

Correct me if I'm wrong, but last I checked the discharge rate on most batteries is quite limited, at least in part due to the chemical and consequently thermal interactions that take place in the process, so this wouldn't really help unless you want the charging station to explode when someone wants to recharge their car. A supercapacitor would be a different story, but that's not practical at this point either.

This. Most batteries have specific rates they can be efficiently charged at, without damaging - and specific discharge rates.

I don't know the specs for Lithium Ion, but there is a reason laptop powerbricks aren't 200W - the batteries cannot handle that charge rate. I've read that they have similar charging curves to lead acid.

One tech that I've wondered if it could be adapted (probably not, because it hasn't already) is AGM (Absorbed Glass Matt), which I have in my RV. I don't recall the specifics, but normal lead acid car batteries (also often used in Deep Cycle marine or RV) can be charged at only 1/4 discharge capacity. So, with a "fast" charge, it takes 4x as long to charge as its max rated discharge.

AGM, on the other hand, theoretically has no limits. I can charge my RV battery at 4x discharge rate, so 16x as fast as a lead acid battery - and more, and I'd need a bigger power source (not that the battery is the limiting factor). Sure, it cost like 3x as much, but worth it.

I've got a bypass on my camper's converter, so I hook my generator up, fire it up, and pump 12V through the camper's "normal" power (to power lights, etc), and another 70 amps (at 12v) straight into the battery... which is a 100Ah @ 12V battery... so fully charged in 1.5 hours.

OK, the thing with lead acid batteries is, charging causes the water to breakdown so you end up releaseing hydrogen. Not much of a problem for batteries you can refill like typical car batteries(flooded type), BIG problem for both sealed types AGM and Gel Cel batteries. You will always get some electrolysis when charging the lead acid battery. The flooded type have catalysts in the caps to recombine the gases to water and any extra just escapes. For sealed types you have a releaf valve that will keep you from building up any dangerous amounts inside the battery. So sealed types will let small amounts recombine, but fast charging will put the sealed types past their safety pressure and you lose your electrolyte (and therefore your capacity).

AGM is a special little beast because the glass matt lets you get away with using less electrolyte, and is why they are called occasionally called dry cell or starved electrolye (2-5% of the electrolyte is removed from the mat before they are finished, so they pretty much don't leak because they mat could still absorb more acid. AGM also uses lead-calcium so that's what's really letting you get away with faster charging times. The MAX potential recharge rate is lower, the calcium adds resistance, but the fact that the calcium helps with the whole electrolysis problem, you can get away with safely recharging it faster.

The difference you get from deep cycle types you mentioned, is they have fewer but thicker plates and lets them handle discharging down to 80% better (still stopping at 50% will give you best life*shrug*). For Starter batteries, they have many thin plates in starter batteries let them pull more current but the thin plates corrode quicker (the sulfur in the acid coats the plates) and can't handle the deep cycles.

Excellent Article. I really liked the intro before the meat of the article.

A note about batteries. If one is looking for a green alternative to internal combustion engines, electric cars really are not the answer. Sure there is less CO2 but the damage caused from producing and disposing of the batteries themselves is really not a net victory. The CO2 is probably easier to deal with.

Thats why I am excited for this technology. I counted batteries out but maybe this could actually be less damaging as well as being a better battery.

Still my money is on gm algae producing biofuels as they can work on our current infrastructure. And hey, produce more biofuels then you need and you reduce atmospheric CO2.

In fact, the thing that's actually made the electric car practical is not the batteries, but the inverters. IGCT's have *dramatically* changed the nature of the problem, and resonant conversion might do the same again.

drag wrote:

If people think that locating refining fossil fuels is a insurmountable problem long-term then they haven't seen what it takes to produce lithium batteries...

I have, up close and personal. What is this problem you refer to?

How are you going to find enough lithium to power over two hundred million cars, trains, and trucks? How many times can you do that in a decade?

Because you are going to have to come up with a scheme to completely replenish the nation's supply of lithium batteries every 5 to 10 years. Since batteries wear out. The faster you charge them the faster they wear out, the more times you charge them the faster they wear out, the closer you get to their capacity each time you use them the faster they wear out.

That's the problem I am talking about.

IF you only drive a less then a hundred miles a day. IF you can afford to spend 4-8 hours charging your vehicle a day. IF you do not need to make long trips, and IF you can afford to swap out your worn out batteries for new ones after x so many thousand charges THEN electric car may work out well for _you_ using current technology. But it's a long long way off from being close to viable solution for the rest of the planet.

How are you going to find enough lithium to power over two hundred million cars, trains, and trucks? How many times can you do that in a decade?

Because you are going to have to come up with a scheme to completely replenish the nation's supply of lithium batteries every 5 to 10 years. Since batteries wear out. The faster you charge them the faster they wear out, the more times you charge them the faster they wear out, the closer you get to their capacity each time you use them the faster they wear out.

Using a battery does not destroy the lithium atoms. When the battery no longer holds a charge, the lithium is still present. Now, if you are planning on taking all of the used batteries and dropping them into a subduction zone, it might be a problem. If, on the other hand, you would like to make new batteries, recovering the lithium and reusing it is not that technically challenging.

If you have enough energy (electricty) there are processes we can do so that restoring the lithium to a near purity will be no problem. We just need a cheap enough electric source so it's a cost effective process..... Anyways, I think it's funny people focus on things like lithium. The storage medium can change and will evolve with time, in those 30 years of replacing whatever battery type, we may have Doped nanotube plates that don't corrode and are generated from the CO2 in the air. Then we don't have to worry(except for the electrolyte), or capacitors could hit the energy density we want.

What's more of an issue is....wait for it....Copper... Yes, your every day copper make become as valuable as silver the only better metal for electronics. Every motor, every generator, in powerplants, homes, and transmission lines, whether it is in your car or in a wind turbine,copper being used transmit and transduce your energy into useful work. To make the mining economical...it usually is done in a manner that would make even an indifferent person blush, like...strip mining. The Good easy ores are already getting harder to find anyways.

I still vote for hydrogen. It was already shown that storing hydrogen in packs of tiny glass tubes like long chunks of honeycomb makes for a reasonably safe storage method. Oooo and I don't think gorilla glass was around at the time either.....

What's more of an issue is....wait for it....Copper... Yes, your every day copper make become as valuable as silver the only better metal for electronics. Every motor, every generator, in powerplants, homes, and transmission lines, whether it is in your car or in a wind turbine,copper being used transmit and transduce your energy into useful work. To make the mining economical...it usually is done in a manner that would make even an indifferent person blush, like...strip mining. The Good easy ores are already getting harder to find anyways.

small correction, most high voltage transmission lines are made of Aluminum due to weight savings (1/2 the weight as compared to a similar rated copper wire).

"Commercial Lithium ion batteries are approaching their theoretical maximum energy storage density, which is lower than that of gasoline by a factor of about 60-70. In the meantime, we want electric cars like the Tesla—but lighter, with longer range and faster recharging times."

What, did you miss the whole graphene laced lithium ion battery discovery? 10 times the storage capacity with equal charge times, or 10 times shorter charge times at current capacities. Assuming they can mass produce it of course.

Hell yeah battery technology. I swear that between awesome batteries, advanced thin-film solar power and the smart-grid upgrades, in 20 years everyone is going to be slapping their foreheads at how stupid everything (is now) used to be.

Even if it is 75 cycles but each cycle gets you 1000 miles of range, then it's not that bad.BTW, the claim:Commercial Lithium ion batteries are approaching their theoretical maximum energy storage density, which is lower than that of gasoline by a factor of about 60-70.

is misleading. Commercial Lithium Cobalt batteries have that sort of density and are reaching their theoretical limits, but the theoretical limit for a "Lithium Ion" battery is about ten times higher. It is just not possible with Lithium Cobalt, which is what is most commonly used in commercial batteries. But mixing "commercial" with "theoretical limit" doesn't make much sense.